This invention relates to a thin film magnetic head wherein head elements such as magnetic cores, windings, etc. are composed of thin layers placed on a substrate by thin film technology, and more particularly pertains to a multi-track magnetic head which is constructed by forming a plurality on unit thin film magnetic heads of the same substrate.
A thin film magnetic head generally has a basic construction in which a magnetic material layer is deposited on a substrate of magnetic material, with a conductor layer interposed therebetween. The substrate and the magnetic material layer constitute a magnetic circuit, the rear end of the layer being magnetically connected to the substrate and the front end being magnetically separated from the substrate to form a recording gap. Electric current is caused to flow through the conductor for recording. The current intensity must be sufficient to magnetize the magnetic medium such as a disc, tape, drum, etc. The cross-section of the conductor layer, however, is small, so that it is not adequate to carry a large current. However, when the heads of a multi-track head comprising a plurality of such unit heads are energized, the total current required is quite large.
To solve such problems, it has been suggested provide a bias conductor layer for supplying, recording bias to the unit heads in addition to a signal conductor layer for supplying signal current to each unit head respectively. Such a bias conductor layer can be constructed as shown in FIG. 2, for example. Referring to FIG. 2, the area of each unit head is defined by a magnetic material layer 2 deposited on a substrate 1. A separate signal conductor layer 3 is provided for to each unit head. A bias conductor layer 4 is provided in the same plane as the signal conductor layer and extends through a plurality of the unit heads.
The cross-sectional view of construction of a conventional head having such a plan view construction is shown in FIG. 1. Referring to FIG. 1, numeral 101 designates a substrate, and a signal conductor layer 103 and a bias conductor layer 104 are deposited on the substrate 101, with a gap 106 therebetween. A magnetic material layer 102 is deposited over the two layers 103 and 104, an insulator layer 105 being interposed therebetween.
In such a construction, however, recording efficiency is very low, because, only a small signal magnetic flux can be obtained at the front gap portion even if a large current flows through the signal conductor layer 103. Therefore it has not been applicable for practical use.
The cause of the low efficiency is that the distance between the magnetic material layer 102 and the substrate 101 is small at the gap 106. The existence of this small distance causes magnetic short-circuit; that is to say, magnetic flux generated by the signal conductor layer is shorted between layer 102 and substrate 101 at the gap portion, so that such flux is not transmitted to the front gap portion for recording.